Saturday, September 24, 2016

An Overriding Influence: Sex determination

When expecting a baby, the most frequent question that pops into the expecting-parents minds is: Is it a girl, or a boy?

At a certain stage in the trimester, doctors can usually give a confident answer to that question. However, 1 in 1,000 babies are born with some gender ambiguity. Many doctors are unable to determine the sex of the child when it looks like the baby has a penis but there is little or no scrotum. This confuses doctors because they are unsure if thy are seeing a boy with undescended tests, or a girl with an enlarged clitoris. Some newborns are even born with external genitals of a boy but have the female ovaries inside.

Excitingly however, researchers are getting closer to determining the gene that can disrupt the normal development of male genitals. Knowing this information helped discover that the action of that gene is responsible for reversing the sex of the fetus, from male testes and a penis, to a vagina and ovaries.

This gene, the maleness gene, is called the SRY gene. It's found on the X chromosome, and it is powerful enough to override the Y chromosome, and take its place. However, when studied in patients there were many contradictions to what they thought they knew. May scientists are now realizing that sex determination is a lot more complicated than they thought.


  1. After discovering if the fetus has the gene that can reverse the sex what do they do next? Is this just more helpful in determining the sex of the child or can something be done with the knowledge of the fact that that gene is present? Also does the gene have negative effects?

  2. If the gene can disrupt/reverse the sex of the fetus in terms of its genitals, does it also reverse other things related to the sex? For example, will height, facial hair growth, and hormone levels be affected later on in a person whose SRY gene has reversed the sex of the person?